Capacitor discharge ignition system

ABSTRACT

An improved capacitor discharge ignition system which produces controlled multiple ignition sparks for each opening of the distributor breaker points. Upon applying a direct current potential across the input terminals of a conventional DC to DC inverter circuit, the inverter power transistors begin oscillating, thereby driving the primary of the inverter transformer which produces a high voltage potential in the secondary windings. A diode bridge circuit rectifies this potential which is applied to a storage capacitor in series with the primary winding of a conventional ignition coil. When the storage capacitor reaches a predetermined voltage potential the silicon controlled rectifier control transistor is forward biased due to the voltage at the junction of a fixed resistor and variable resistor which are in series and connected across the high voltage supply. Upon opening of the distributor breaker points, a capacitor in series with the collector of the control transistor begins to charge causing a current flow through the gate cathode junction of the silicon controlled rectifier sufficiently to forward bias the anode cathode junction of the SCR. The storage capacitor discharges through the SCR and primary of the ignition coil causing an ignition spark to be produced. This discharge of the storage capacitor causes the base potential of the control transistor to drop to zero volts thereby raising the collector emitter resistance which reduces the SCR gate current flow below trigger level, and due to the zero potential between the anode and cathode electrodes of the SCR. the SCR turns off. Immediately the storage capacitor starts to recharge and again upon reaching a predetermined voltage potential, the circuit repeats as stated above to produce another ignition spark, provided the previously mentioned capacitor in series with the control transistor&#39;&#39;s collector has not reached a charged state which would prevent sufficient SCR gate trigger current. The capacitor&#39;&#39;s RC time constant is controlled by a variable resistor which may be adjusted to produce from one to as many ignition sparks as desired, depending on the frequency of the ignition sparks as determined by the variable resistor associated with the base electrode of the control transistor and the duration of the opening of the breaker points. Upon closing of the breaker points, the control transistor&#39;&#39;s collector capacitor is discharged through the breaker points and a fixed resistor thereby resetting the circuit for the next ignition cycle.

United States Patent 1 Posey Feb. 27, 1973 CAPACITOR DISCHARGE IGNITIONSYSTEM [76] Inventor: Thad W. Posey, 2402 Apple Hill Rd., Alexandria,Va. 22308 [22] Filed: April 5, 1971 [21] Appl. N0.: 130,950

[52] US. Cl. ..l23/l48 E [51] Int. Cl ..F02p 3/06 [58] Field ofSearch..173/l48 E [56] References Cited UNITED STATES PATENTS 3,620,20111/1971 Warren ..l23/l48 E 3,383,556 5/1968 Tarter ...l23/l48 E3,489,129 1/1970 Issler et a1. ..l23/148 E 3,626,910 12/1971 Porsche....123/148 E 3,277,340 10/1966 Jukes et a1. ....123/l48 E 3,386,0005/1968 Farr ....123/148 E 3,367,314 2/1968 Hirosawa et al. ..123/148 EPrimary ExaminerLaurence M. Goodridge Assistant ExaminerCort R. Flint [57] ABSTRACT ignition coil. When the storage capacitor reaches apredetermined voltage potential the silicon controlled rectifier controltransistor is forward biased due to the voltage at the junction of afixed resistor and variable resistor which are in series and connectedacross the high voltage supply. Upon opening of the distributor breakerpoints, a capacitor in series with the collector of the controltransistor begins to charge causing a current flow through the gatecathode junction of the silicon controlled rectifier sufficiently toforward bias the anode cathode junction of the SCR. The storagecapacitor discharges through the SCR and primary of the ignition coilcausing an ignition spark to be produced. This discharge of the storagecapacitor causes the base potential of the control transistor to drop tozero volts thereby raising the collector emitter resistance whichreduces the SCR gate current flow below trigger level, and due to thezero potential between the anode and cathode electrodes of the SCR. theSCR turns off. Immediately the storage capacitor starts to recharge andagain upon reaching a predetermined voltage potential, the circuitrepeats as stated above to produce another ignition spark, provided thepreviously mentioned capacitor in series with the control transistorscollector has not reached a charged state which would prevent sufficientSCR gate trigger current. The capacitors RC time constant is contro ledby a variable resistor which may be addischarged through the breakerpoints and a fixed :resistor thereby resetting the circuit for the nextignition cycle.

3 Claims, 1 Drawing Figure CAPACITOR DISCHARGE IGNITION SYSTEM SUMMARYOF THE INVENTION This invention pertains to an improved capacitordischarge ignition system specifically for but not limited to theinternal combustion engine requiring timed ignition sparks. The intentof this invention is to improve the combustion process of an internalcombustion engine by employing unique circuit means to producecontrolled multiple ignition sparks for each ignition cycle therebyimproving the efficiency of the engine and reducing exhaust emissionsdue to poor and incomplete internal combustion.

It has been determined that prior single spark capacitor dischargeignition systems may produce a spark of relatively short duration whichwill not ignite certain cylinder charge mixtures properly for goodcombustion. Other suggested continuous firing ignition arrangements whenused with the conventional automotive distributor do not provide meansto adequately control the continuous ignition sparks to guard againstpre-ignition at high engine revolutions per minute.

The object of this invention is to employee circuit means which canproduce multiple ignition sparks where the second ignition spark isproduced approximately 400 microseconds after the initial ignition sparkof a given cycle, which effectively results in a longer ignition spark.This is accomplished by taking advantage of the ignition coilsinductance to recharge the storage capacitor after an initial dischargethrough the ignition coil. Additional ignition sparks are producedthereafter depending on circuit means adjustment for spark frequency andcircuit means adjustment for quantity of sparks desired for eachignition cycle.

DESCRIPTION OF DRAWING The schematic drawing shows a preferred circuitdiagram of the invention with numerical designators depicting circuitcomponents.

DETAILED DESCRIPTION Referring to the schematic diagramit will be notedthere are three major sections of which comprises the entire system.They are, the DC to DC inverter circuit which is commonly used toconvert a lower voltage direct current source to a higher voltagesource; the controlled trigger circuit which controls the electronicswitch, and the spark discharge circuit made up of a high voltagestorage ignition capacitor and a silicon controlled rectifier used inthis circuit as an electronic switch.

The following description explains the operation of this circuit indetail: Upon applying a positive voltage to input battery terminal 16and a negative voltage to input battery terminal 17 which is grounded,the two power transistors 13 and 14 begin oscillating, driving theprimary of the transformer 12. Bias resistors and 1 l aid in startingthe inverter circuit when power is first applied and oscillator drivewinding 15 sustains inverter drive once the circuit has started.Secondary winding 18 is magnetically coupled to the primary winding 12and due to the turns ratio, the secondary winding 18 will have inducedacross its winding approximately 550 volts. Diode bridge 19 rectifiesthis potential into a direct current source and starts charging storagecapacitor 41 which is in series with the primary winding of the ignitioncoil 42 to ground. A fixed resistor 21 and a variable resistor 23 areconnected in series 22 and across the high voltage source 20 and 17. Atthe junction 22 of the two resistors 21 and 23 is connected the baseelectrode 25 of the SCR control transistor 27. As the storage capacitor41 charges, the potential at junction 22 as determined by variableresistor 23 raises to suflicient value to forward bias controltransistor 27. Upon opening of the distributor breaker points 44,trigger capacitor 32 begins to charge from the positive low voltagebattery 16 through current limiting resistor 33 and through thecollector 26, emitter 24 of transistor 27, through resistor 34, andthrough the gate 37, cathode 38 of silicon controlled rectifier 39 andthrough diode 45 to ground. This current flow through the SCR gate 37forward biases the SCR anode 40, cathode 38 junction thereby turning onthe SCR 39 which discharges the storage capacitor 41 through diode 45 toground 17, and through the primary of the ignition coil 42 to ground 17producing an ignition spark. This on" condition of the SCR 39 also shortcircuits the high voltage supply 20 to ground 17 which stops inverterdrive and drops the junction 22 and base electrode 25 of controltransistor 27 to zero volts which raises the collector 26, emitter 24junction resistance thereby reducing SCR gate 37 current flow below SCR39 trigger level. Immediately SCR 39 turns off due to the zero voltspotential between the SCR anode 40 and cathode 38. The inverter circuitagain starts as previously described and begins recharging the storagecapacitor 41. Again when the voltage potential at junction 22 reaches avalue sufficient to forward bias control transistor 27 and providedtrigger capacitor 32 has not reached a charged state through variableresistor 28 and diode 30, the SCR 39 will turn on and discharge thestorage capacitor 41, producing another ignition spark as previouslydescribed. The circuit will continue to repeat this firing cycle asdescribed above during the entire duration of the breaker points 44opening. Upon closing of the breaker points 44, the positive charge oncapacitor 32 is discharged through fixed resistor 29 and diode 31 andthrough the breaker points 44. This fixed resistor 29 and diode 31provide a fixed time constant which controls the trigger capacitor 32discharge, thereby requiring a predetermined breaker points 44 closureduration prior to opening, eliminating firing the SCR 39 on breakerpoint 44 bounce. As long as breaker points 44 remain closed the triggercapacitor 32 cannot charge therefore the SCR 39 cannot go intoconduction even though the control transistor 27 may be forward biaseddue to the voltage potential at junction 22 which causes a base 25,emitter 24 small current flow below SCR 39 trigger level.

Variable resistor 28 may be adjusted to control the charge time oftrigger capacitor 32 providing from one to multiple firing of the SCR 39for each opening of the breaker points 44. Variable resistor 23 may beset to forward bias the control transistor 27 at various voltagepotentials applied to the storage capacitor 41. In this way thefrequency and power of the ignition sparks may be controlled as well asthe number of sparks per breaker point 44 opening.

Previously unexplained diode 45 is used to aid in turning off the SCR39, by clamping the cathode 38 of the SCR 39 slightly positive duringconduction of the SCR 39. Resistor 35 is used to establish a groundpotential on the gate 37 of SCR 39 during the off condition of the SCR39. Capacitor 36 is used to filter out transient noise spikes on thegate 37 of the SCR 39 for protection against false firing of the SCR39.. Resistor 34 is used to aid in turning off the control transistor 27when the base 25 voltage drops near zero volts.

Extensive testing of this circuit has revealed very good performance canbe achieved by setting variable resistor 23 to forward bias controltransistor 27 at approximately 300 volts charge on the storage capacitor41. This will take advantage of the energy returned to the storagecapacitor 41 by the inductance of the igni- -tion coil 42 when thestorage capacitor 41 has been discharged through the ignition coil 42from approximately 550 volts on the initial opening of the breakerpoints 44. The coils inductance will recharge the storage capacitor 41to approximately 300 volts in approximately 400 microseconds and producea second spark which effectively results in a longer ignition spark oninitial breaker points 44 opening. Additional sparks will be produced ata somewhat longer time interval depending on the power supply restartcapability etc., and may also be controlled by variable resistor 28 toshorten the charge time of trigger capacitor 32 to limit the number ofsparks per breaker point 44 opening.

Tests have also revealed that excessive ignition sparks during breakerpoint 44 opening may result in pro-ignition at high engine revolutionsper minute due to the relative position of the distributor rotor buttonjust prior to breaker point 44 closure. It is therefore essential that ameans to limit the number of ignition sparks per breaker point 44opening be provided as described in the preceding disclosure for properoperation of an internal combustion engine.

The foregoing description of the invention as related to test andperformance have been made in accordance with application statutes andis not intended to limit this invention, but merely as being descriptivethereof.

I claim:

1. A multiple firing capacitor discharge ignition system for internalcombustion engines comprising an ignition coil with primary andsecondary windings; spark initiation means timed to the relativeposition of the engine's pistons; a source of DC voltage; a DC to DCinverter circuit to convert a lower voltage source to a high voltagesource with a diode bridge circuit to rectify this high voltage to adirect current source; a storage capacitor with one side connected tosaid high voltage source and the other side to the primary of saidignition coil; a silicon controlled rectifier with its anode connectedto said high voltage source, its cathode connected to ground, its gateconnected to circuit means connected to the base of a silicon controlledrectifier control transistor; a second circuit means adapted to controlthe silicon controlled rectifier comprising said silicon controlledrectifier control transistor with its emitter connected to the gate ofthe said silicon controlled rectifier; a third circuit means adapted toinitiate an ignition spark and limit the number of ignition sparks perbreaker points opening consisting of a silicon controlled rectifiertrigger capacitor with one side connected to the collector of the saidsilicon controlled rectifier control transistor and a variable resistorand diode in series to ground and a fixed resistor and diode in seriesto ground, whose values determine the charge and discharge time of saidtrigger capacitor, thereby controlling the number of ignition sparks perbreaker points opening, and the other side of the trigger capacitorconnected to the said low voltage positive battery terminal through aresistor and breaker points connected at the resistor capacitor junctionoperating to ground. 1

2. A system according to claim 1 wherein said first circuit means tocontrol the frequency and energy of said multiple ignition sparksconsists of a voltage divider with a fixed resistor and variableresistor connected across the high voltage DC supply, whose valuesdetermine the ignition spark frequency and spark energy by allowing thesaid silicon controlled rectifier control transistor to trigger the saidsilicon controlled rectifier only after the said storage capacitorreaches a predetermined voltage charge.

3. A system according to claim 1 wherein said second circuit means tocontrol the silicon controlled rectifier consists of a transistor withits base connected to the junction of said voltage divider, emitterconnected to the silicon controlled rectifier gate and collectorconnected to a trigger capacitor. The said silicon controlled rectifiercontrol transistor circuit so arranged will upon breaker points openingprovide trigger current to the gate of the said silicon controlledrectifier until the silicon controlled rectifier turns on dischargingthe said storage capacitor which turns off the silicon controlledrectifier control transistor thereby removing the silicon controlledrectifier gate trigger current.

1. A multiple firing capacitor discharge ignition system for interNalcombustion engines comprising an ignition coil with primary andsecondary windings; spark initiation means timed to the relativeposition of the engine''s pistons; a source of DC voltage; a DC to DCinverter circuit to convert a lower voltage source to a high voltagesource with a diode bridge circuit to rectify this high voltage to adirect current source; a storage capacitor with one side connected tosaid high voltage source and the other side to the primary of saidignition coil; a silicon controlled rectifier with its anode connectedto said high voltage source, its cathode connected to ground, its gateconnected to circuit means adapted to produce multiple triggers to thesaid silicon controlled rectifier for each breaker points opening; afirst circuit means adapted to take advantage of the energy returned tothe said storage capacitor after an initial ignition spark therebyproviding a second ignition spark approximately 400 microseconds afterthe first spark and means to control the frequency and energy of saidmultiple sparks thereafter comprising a voltage divider circuit betweenthe said high voltage supply and ground with the voltage dividerjunction connected to the base of a silicon controlled rectifier controltransistor; a second circuit means adapted to control the siliconcontrolled rectifier comprising said silicon controlled rectifiercontrol transistor with its emitter connected to the gate of the saidsilicon controlled rectifier; a third circuit means adapted to initiatean ignition spark and limit the number of ignition sparks per breakerpoints opening consisting of a silicon controlled rectifier triggercapacitor with one side connected to the collector of the said siliconcontrolled rectifier control transistor and a variable resistor anddiode in series to ground and a fixed resistor and diode in series toground, whose values determine the charge and discharge time of saidtrigger capacitor, thereby controlling the number of ignition sparks perbreaker points opening, and the other side of the trigger capacitorconnected to the said low voltage positive battery terminal through aresistor and breaker points connected at the resistor capacitor junctionoperating to ground.
 2. A system according to claim 1 wherein said firstcircuit means to control the frequency and energy of said multipleignition sparks consists of a voltage divider with a fixed resistor andvariable resistor connected across the high voltage DC supply, whosevalues determine the ignition spark frequency and spark energy byallowing the said silicon controlled rectifier control transistor totrigger the said silicon controlled rectifier only after the saidstorage capacitor reaches a predetermined voltage charge.
 3. A systemaccording to claim 1 wherein said second circuit means to control thesilicon controlled rectifier consists of a transistor with its baseconnected to the junction of said voltage divider, emitter connected tothe silicon controlled rectifier gate and collector connected to atrigger capacitor. The said silicon controlled rectifier controltransistor circuit so arranged will upon breaker points opening providetrigger current to the gate of the said silicon controlled rectifieruntil the silicon controlled rectifier turns on discharging the saidstorage capacitor which turns off the silicon controlled rectifiercontrol transistor thereby removing the silicon controlled rectifiergate trigger current.